The paperboard container having a fitment, or pour spout, from which the liquid inside may be easily poured therefrom is fast becoming a standard in the milk and juice carton industry. In order to place a fitment on the typical paperboard container a hole must first be punched or cut out of the carton's surface. The presence of this hole increases the complexity of the sterilization process.
FIG. 1 presents a schematic crossection of typical prior art apparatus for sterilizing paperboard material used for liquid containers. An application roller rotatingly dips into a reservoir of sterilant, typically hydrogen peroxide. The paper board stock to be sterilized is passed through a nip between the application roller and the back up roller thereby flooding the hydrogen peroxide upon the surface of the paperboard. The flooded paperboard is then passed through a nip between the back up roller and doctor roller whereby excess hydrogen peroxide is removed from the paperboard and drips back into the reservoir.
Although this process has worked well for paperboard having a continuous surface without holes therein, for the receipt of a fitment, the doctor roller/backup roller combination is unable to remove the excess sterilant that collects within the gap, or opening, presented between the doctor roll and the backup roller by the presence of the fitment hole. Thus as the sterilized paperboard is discharged from the doctor roller/backup roller nip the accumulated sterilant, within the fitment hole flows across the paperboard leaving an undesired residual of sterilant upon the board. Similarly, for paper board having surface irregularities such as score lines etc. the prior art method of sterilization causes a build up of sterilant in the areas of surface area height differentials thereby leaving globules or droplets of sterilant upon the paperboard surface. Subsequently the, system used to dry the sterilant from the board is unable to dry the residual sterilant and many times producing a sterilized paperboard having a hydrogen peroxide residual greater than 0.5 parts per million, the industry standard.